摘要:

The ionized impurity limited momentum relaxation time for carrier scattering within a quantum well wire is calculated for both infinite and finite confining wells models. The transverse part of the carrier wave function is taken to be a Bessel function. For a background impurity distribution, the scattering frequency increases with increasing well depth. For remote ionized impurities or a tube of impurities the scattering frequency decreases with increasing well depth. We assume GaAs/Ga1−xAlxAs for the material of the quantum well wire structure.

ISSN:0734-211X    

DOI:10.1116/1.583403

出版商:American Vacuum Society    

年代:1986

数据来源: AIP

摘要:

Chemical sputtering yields of silicon resulting from the incidence of isotopically pure19F+,35Cl+, and81Br+ion beams were measured in the 100–3000 eV energy range. It is found for these cases that the chemical sputtering yields saturate in the high energy range of more than 600 eV. The saturated yields (atoms/ion) are 0.18 for F+/Si, 0.45 for Cl+/Si, and 0.23 for Br+/Si. The yields increased with increasing ion energy in the 100–500 eV region with different slopes. The steepest slope is observed for the case of Br+/Si, and the smallest is the F+/Si case. This difference in the slope indicates that the chemical reaction between Br+and Si cannot be activated without high acceleration of Br+, and the same occurs for Cl+/Si. On the other hand the F+ion is assumed to react with Si with a relatively high probability even when the energy is low. On the basis of these results, a reactive spot model is proposed for the ion‐assisted chemical etching process. A generalized method to get anisotropic profiles is also presented for reactive ion etching of Si with fluorine‐, chlorine‐, and bromine‐containing gases.

ISSN:0734-211X    

DOI:10.1116/1.583404

出版商:American Vacuum Society    

年代:1986

数据来源: AIP

摘要:

Silicon etch rates in CF4/O2plasma have been studied in a diode reactor which allows both reactive ion etching (RIE) and plasma etching. A fluorine population was also measured from the intensity of optical emission in conjunction with argon actinometry, in order to separate etch rates contributed by the ion enhanced etching and the spontaneous chemical etching. A heavily dopedn‐type silicon etches faster than undoped silicon, while a heavily dopedp‐type silicon etches slower than undoped silicon. Although this doping effect is present in both ion enhanced etching and chemical etching, it is a more severe influence in the isotropic chemical etching. The thermal activation energy for the chemical etching was measured to be 0.10 eV, independent of the chemical and electrical properties of dopants. The Coulomb attraction between uncompensated donors (As+) and chemisorbed halogens (F−) enhances etch rates in a heavily dopedn‐type silicon, whereas the Coulomb repulsion between uncompensated acceptors (B−) and chemisorbed halogens (F−) inhibits etch rates in a heavily dopedp‐type silicon.

ISSN:0734-211X    

DOI:10.1116/1.583405

出版商:American Vacuum Society    

年代:1986

数据来源: AIP

摘要:

Studies were conducted to investigate the properties of the Ru–GaAs interface. An analysis was made of two sets of experimental findings, namely the distribution of surface states of GaAs covered by submonolayers of ruthenium, as well as of electrical measurements on Ru–GaAs contacts. It was found for the present case that a deep state nearEt≊0.3 eV above valence band maximum is induced at the surface. Thus the influence of the intrinsic defects is at least compensated. Using a simple model, it was investigated to which degree surface states and their energy would govern the barrier height. It was further studied how Fermi level pinning depends on the doping concentration of the semiconductor.

ISSN:0734-211X    

DOI:10.1116/1.583407

出版商:American Vacuum Society    

年代:1986

数据来源: AIP

摘要:

This paper deals with an automatic linewidth measurement method of photoresist pattern linewidths with high accuracy, which we call ‘‘the linear regression method.’’ In the linear regression method, the secondary electron intensity profile at the photoresist pattern edge is approximated by two lines. One is the average line of the secondary electron intensity profile on the substrate and another is the slope line corresponding to the slope of the photoresist edge. The cross point of the two lines is defined as the pattern edge. The linewidths obtained by this method agree with the linewidths obtained by the cross sectional SEM images which are defined as true values, within 0.009 μm for various photoresist slope angles and within 0.002 μm for variation of the underlying materials. A practical pattern linewidth measuring apparatus which employs a high speed measurement time of 2.34 s is also described.

ISSN:0734-211X    

DOI:10.1116/1.583408

出版商:American Vacuum Society    

年代:1986

数据来源: AIP

摘要:

Plasma copolymerized methylmethacrylate and tetramethyltin [PP(MMA–TMT)] was prepared using an inductively coupled gas flow‐type reactor. The atomic ratio of tin to carbon (Sn : C) in PP(MMA–TMT) was varied from 0 to 0.15 by changing the gas flow rate ratio of both TMT and MMA monomers. The characteristic of PP(MMA–TMT) as a resist was evaluated in dry lithography processes, in which the resist was exposed to radiation of CuKα(main wavelength: 1.54 Å) and x‐ray imaged pattern in the resist was developed by Ar–20% O2mixture gas plasma using a parallel plate electrode‐type reactor. The sensitivity of positive resist was defined by the minimum dose rate that the resist in the exposed part was etched off when the remaining thickness at the unexposed part became about 38% of the initial film thickness under the plasma development. PP(MMA–TMT) resist showed the highest sensitivity of 8 J/cm2at Sn : C of 0.046. The molecular structure of PP(MMA–TMT) film was investigated by electron spectroscopy for chemical analysis (ESCA) and infrared (IR) analysis and discussed in relation to its quality as a resist.

ISSN:0734-211X    

DOI:10.1116/1.583409

出版商:American Vacuum Society    

年代:1986

数据来源: AIP

ISSN:0734-211X    

DOI:10.1116/1.583410

出版商:American Vacuum Society    

年代:1986

数据来源: AIP

摘要:

Electrical measurements have been made on films of lightly Si‐doped GaAs and on (AlGa)As/GaAs two‐dimensional electron gas (2DEG) structures grown by MBE. These have shown residual donor and acceptor concentrations of ∼2×1014cm−3in the GaAs, and mobilities for 2DEG layers which varied systematically with carrier densitynsand undoped spacer layer thicknessd; the highest mobility obtained was 2.2×106cm2 V−1 s−1for a sample withns=2×1011cm−2andd=800 Å. Analysis of the data shows that scattering by remote ionized impurities is the dominant mechanism in most of our 2DEG samples. In such layers, the mobility μ at 4 K varied with photoexcited carrier densitynsapproximately asns1.5. This behavior is expected for photoexcitation of carriers from DX centers in the doped (AlGa)As, and results from increased screening in the 2DEG and increased scattering due to the greater number of charged impurities in the (AlGa)As. However, some samples showed a much steeper variation of μ withns, and also different temperature dependences of μ for high and lownsvalues. Comparison with previously reported data on Si–SiO22DEG systems suggests that this effect is due to strong localization effects occurring at the (AlGa)As–GaAs interface.

ISSN:0734-211X    

DOI:10.1116/1.583411

出版商:American Vacuum Society    

年代:1986

数据来源: AIP

ISSN:0734-211X    

DOI:10.1116/1.583412

出版商:American Vacuum Society    

年代:1986

数据来源: AIP

摘要:

We have found that AlGaAs films grown by molecular beam epitaxy on (110) orientation tend to segregate to their constituent binaries on an extremely fine scale. However, the microscopic segregation in AlGaAs does not impede its capability of providing suitable, macroscopic barriers in the formation of heterostructures. High mobility two‐dimensional electrons and holes in modulation‐doped AlGaAs/GaAs(110) heterojunctions are demonstrated for the first time, with obvious implications for the combined growth of IV and III–V materials.

ISSN:0734-211X    

DOI:10.1116/1.583413

出版商:American Vacuum Society    

年代:1986

数据来源: AIP